Oslo’s Photoncycle raises €15 million to enable households to store surplus summer solar power for winter use

Photoncycle, an Oslo-based energy storage scaleup, has raised €15 million in Series A funding to enable households to store surplus summer solar power for winter heating and electricity.

The round was led by NordicNinja and Voima Ventures, with participation from existing investors Lifeline Ventures, Eviny Ventures, Luminar Ventures, and Momentum.

“Europe is beginning to solve short-duration storage. The remaining gap is seasonal. If households can store summer energy for winter use, they reduce exposure to imported fuel and price volatility as well as to increasing grid costs for consumers,” said Bjørn Brandtzæg, founder and CEO of Photoncycle.

Founded in 2020 by Brandtzæg, Photoncycle claims to be building the distributed storage infrastructure for Europe’s renewable energy future. The company develops solid-state hydrogen energy storage systems that enable households and businesses to store summer solar power for winter use. The company’s patented technology converts surplus renewable energy into solid-state hydrogen, stored underground, and releases it as clean heat and power when needed.

According to Photoncycle, the investment comes as Europe continues to grapple with the structural vulnerabilities exposed by the 2022 energy crisis. The company states that the EU imported €396 billion of fossil fuels in 2025, around €880 per citizen, underscoring the bloc’s continued dependence on external supply even as renewable generation expands.

It highlighted that winter exposure is especially severe: space heating makes up 62.5% of household energy use, and natural gas remains a major part of residential consumption, making households vulnerable to seasonal fluctuations in global gas prices.

With this fresh capital, the company aims to support the commercial rollout in Denmark and the Netherlands and finance the first phase of an industrialisation plan that includes a proposed 1.4-terawatt-hour annual manufacturing facility.

Photoncycle claims that at full industrial scale, its proposed 1.4 TWh manufacturing facility would have storage capacity equivalent to roughly 140,000 homes, each storing 10,000 kWh of seasonal energy. 

The scaleup’s distributed, household-level seasonal storage aims to lower the amount of imported gas needed for winter heating, thereby decreasing Europe’s dependence on fossil fuel imports during winter.

To lower upfront costs for homeowners, the company intends to offer the system under a subscription-based model covering solar panels, storage, servicing, and access to energy trading markets

Photoncycle reports strong early interest from households looking for alternatives to gas heating. In Denmark, where Photoncycle’s waiting list is growing quickly, energy costs are among Europe’s highest, and 300,000 homes still rely on gas heating, which will be phased out by 2035.

“As the share of renewable energy increases, structural price volatility in electricity markets is rising. Seasonal storage is therefore not a niche solution, but a systemic necessity. Photoncycle addresses this imbalance by enabling households to store energy across seasons and reduce their dependence on imported fossil fuels. This is an important building block for a resilient and sovereign European energy system,” said Inka Mero, founder and Managing Partner at Voima Ventures. 

Photoncycle aims to use this Series A funding to scale manufacturing and early commercial deployment in Denmark initially, followed by Europe’s other large markets, including the Netherlands. Beyond Europe, there are opportunities to scale its technology in Asia, including Japan, and in the US.

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